Electromagnetic relay



Jan. 22, 1929. 1,699,782

J. ERICKSON ELECTROMAGNETIG RELAY Filed July 27, 1925 -hmen [1r- Juhu Ermksnn Patented Jan. 22; ieee. y Midtl JOHN ER'KsON, @F.CHILCAGC, ."L`.Jl\TOIS, ASSGNOR, BY MESNE ASSGNYZEIQ'TS, T0 'UTOMATIC ELECTRIC INC., GF CHICAGO, ILLINIS, A CORZPORLTION 0F BELA- WARE.

ELECTRAGNETIC Application led duly 2?, 1925.. Serial No. 46,2%.

This invention relates in genera` to elecmember 6 against which the armature 3 rests tromagnetic relays, and has iior its principal when the relay is in its normal position. 55 object the provision oi a new7 and improved ln dFigs. 4 and 5, l have shown 'the details relay which attracts its armature when the ci a modification or my invention shown circuit through its coil is broken. in ig. 2, the modiiication being in the nature Elect-romagneticV relays of the orthodox oi an improved magnetic back stop against type attract their armatures when the circuit which the armature rests when the relay is in 6 through their coils is completed, and allow its normal position. This reliv consists oi the armature to retract when the circuit is the core 5f mounted on the neel piece 2 l0 broken. lit frequently happens that circuits around which core is the copper col can be greatly simplified by providing a relay and the winding l. The armature 3 also which tvorls in the opposite direction, that mounted on the heel niece 2 and arranged to is, a relay which remains inert when a curoperate the spring assembly 7 through rent oi normal value is passing 'through its mediumY of the armature lever 3. coil and Whichattractsits armature momenorthodox relay ot this type, the armature tarily Tthen that current is broken. lever 3 normally rests against the noni further object of this invention is the magnetic back stop 9, which is assembled 7a provisionor" a relay Which Will remain inert on the heel piece 2 as a part of the spring when a normal current is oiving through its assembly 'l'. in converting such a relay in coil, but'vvhich will attract its armature to accordance with the objects of this invention, its core should that current become eXcessive- I have replaced this nonmagnetic back stop ly large, or should it become interrupted. 9 by a magnetic back stop of identical shape. 75' Further objects of my invention not spel have also added the magnetic Washer 8 ciiically mentioned here Will be apparent between the copper collarr 4 and the Wind! from the detailed specification and claims ing l of the relay and attached to this Washer Which follow. the magnetic back stop 6', which rests against The drawing comprising Figs. l to 6, inclu# the armature lever 3, when the relay is-in 8G sive, show suiiicient detail to enable a clear its normal position. lt Will be readily seen understanding of my invention. that by equipping this armature back stop Figs. 1,2, and 3 shoW one Way 0i' carrying lever with a slot through which the mountout the invention, Fig. 2 being the complete ing screw extends, l have made it adjustable, y assembly of a. relay and Figs. l and 3 beingthereby facilitating an easy assembly of the 85 details. Figs. 4 and 5 represent a modiicarelay structure. tion, the first illustrating a complete relay, Figure 6 shows a circuit in which the relay and F ig. 5 showing a detail part. Fig. 6 of my invention can rbe used, this circuit beshows a circuit wherein the relay shown in ing shown by Way of example. .4i direct Fig. 2 or that shown in F ig. 4, is utilized. Current motor M is connected to one side of 90 The structure and operation of the invention a source of power 26, through the springs 25, will n'ow be described more in detail. and to the other side of the source of power 40 Referring now particularly to Fig. 2, the 27 through the Winding of relay 2l. The re relay shown comprises the coil l Wound' lay 2l which maybe of the type shown in around the core 5, which is mounted on the Figs. 2 or 4 is so adjusted that when the nor- 95 heel piece 2. This relay will be recognized. mal current consumed by the motor M flows y as the ordinary slow acting relay with a to it, it Will not attract this armature. Should copper slug 4 on the armature end of the core. this current be interrupted or should the mo- Such a relay, when the coil is energized will tor become overloaded and draw an excessive attract theV armature 3`ft`0 the core 5 and opercurrent, the relay 2l Will energize and'open 109 atethe spring 7 in the Well known manner. the circuit of the motor thereby protecting it lar To convert this relay into a relay built in from injury.

o0 accordance with the object of my invention, Having thus described my invention in Ihave added the magnetic Washer 8 between general, l will now proceed with a detailed the copper slug 4 `and the Winding' l, and description of its operation. When the re- 105 attach ,to this Washer.` the magnetic back stop lay shown in Fig. 2 is connected in a circuit cording to Lenzs law,

' comes a north pole,

such as that shown in Fig. 6, and the key r28 opened, the relay 20 restores and at spring 25 closes a circuit from the terminal 26 through the springs 25, the armature of the motor, the Windinglof the relay 21 to the terminal 27. Currentwill start to flow in this circuit, and after an interval Will build itself up to its normal stre'ngtli. In the relay 21, during the interval that the current is building up in the coil 1, there is induced in the copper collar 4, a current which, ae- Hovvs in such a direction that the magnetism which this induced current produces is in opposition to the magnetism setup by the current inthe coil 1. That is, if the current in the coil 1 isin such a direction that the inagnetiewasher 8 bethe current induced in the copper collar e will be in 'such a direction that the face of the collar adjacent to they Washer 8 will also be a north pole. rli'hese tivo north poles are opposing each other and preventing the tree flow otiiux through the coie 5 and into the armature by Way ot the air-gap.v However, the flux set up by the -coil 1 flows through the magnetic Washer 8 thence through the magneticback stop 6 to the armature intothe heel piece 2 and thence back into the coil 1 through the icor'e 5.; The presence of this 'opposing magnetic motive :torce set up by the copper collar 4 prevents any appieciable amount of lux set up by the coil 1 from tiovving through the core 5 an normal air-gap into' the armature 3. Vhen the current in the coil`1 has risen to its maxiiniun value and `s no longer building up, the

currents induced in the copper collar tdie away and consequently there is no opposing stop by the magnetomotive by the coil 1 Hows through the above named magnetic path for the reason that consists solely of iron and virtually short circuits the air-gap. The little tluxthat does 'enter the armature by way of the air-gap is insufficient to attract.the armature ,to the core since the armature is held to the back junction. It Will be seen that as long as the current in the'coil `1 is of such valu-e that the magnetic back stop member 6v is not over y saturated, only a small amount of magnetism will flow through the air-gap from the core into the armature and consequently the armature will not be attracted. -It the motor becomesoverloaded anddraws an excessively large amount of current, the coil 1 Willset up'a niagnetomotive force sufiicient to over saturate themagnetic back stop 6 with the result vthat more flux will flow through the air-gap into'the armature. When this {iux becomes' suiciently strong, the armature4 3 breaks away from the magnetic back stop `6 and is attracted to the core 5r, operating the springs 7 in the obvious mann'er.

might ybe necessary to the magnetic c iicuit Jfrom the core 5 :torce in the copper collar.` However, the majority of the flux produced tha@ path flux now {iovving through thatflowing bridges the air-gap,

As soon as the current f The relay now being operated can be made to operate whatever protecting devices are necessary to prevent the overloaded motor from burning It' the current supply to amotor such as shown in Fig. 6, were to be interrupted, it Y notify an attendant of the tact so that he could take the necessary steps to bring the motor back into service. The relay ot my inventionmay be used for this purpose in much the same manner as the no voltage release of the Well known starting boxes. Then the circuit to the coil 1 is interrupted, the current starts to die away at a rate dependent upon the inductive characteristics of the relay. This dying away of .the current Scauses a corresponding decrease `in the iux, and as a result of this decrease in iuX a current is induced in the coppercollar 4. The direction of the current in this copper collar is opposite to What it was when the current Was building up in the relay, and asa consequence the magnetism set up by the induced current assists rather flux set up by the coil. As Was eX lained betore the current through the cil is in such a direction as to make the magnetic Washer 8 a north pole, and consequently the current induced in the copper collar makes the side of the collar adjacent to this Washer a south pole, and thefside near the end ofthe core 5, a north pole. The two magnetizing forces d i onthe core 5 are now poled in the same direction with the result that 'moreiiux flows over through the air-gap into the armature 3 thence through the heel piece 2 back into the core. .The decay of the flux set Iup by the coil lessens the attraction between the armature and back stop, thereby lessening the amount of flux that must flow through the air-gap to attract the armature tothe core. the flux set up by the slug has two parallel patlistofl travel, both of Which include the airfgap. The first path is from the slug end of the core y5 across the air-gap, through the armature and heel piece into the core, as traced above. The second path is from the slug end of the core 5 through the air-gap into the armature 3, through the back stop 6 into the slug end ot the core. The direction of flow of the slug flux through this path is opposed to the direction of the coil iuX, and neutralizes it. `At tlie. instant the oiv otJ iuX through this back stop path becomes zero,'the attraction between the armature and back stop becomes zero and as allthe flux the armature is attracted to the core.: has completely died away in the Winding 1 of the relay, the currents induced in t-lie copper collar die ayvay andthe relay releases its armature, which returns to normal, unless the circuits are arrange itselt1 in. energized'position. `If the armathan opposes the v Moreover d so that the'relay locks energized, the flux set up by the coil will retain the armature inits operated position.'

Referring now specifically to Fig. 4, which isa modification of Fig. 2, the magnetic back stop check is arranged t'o be in contact with the armature lever 3 rather than the armature proper 3. By this arrangement an advantage of' leverage is obtained. Then the current is building up in the coil l and the induced currents in the copper collar t are opposing this building up of flux, the tlux lows over a circuit including the core 5, the magnetic washer 8".' the back stop 6', the armature lever 8, the armature back stop 9', the heel piece E2 and thence back into the core. Since there is a leverage of approximately two to one ratio in this arrangement, a comparatively small tiux flowing between the back stop 6 and the armature lever 3 will retain the armature in its normal position, as the attraction on the arn'iature 3 by the core must be at least twice as great in order to operate the armature. lWith an arrangement suchas is shown in Fig.4, it is `rdifficult to wind the coil l so that the armature 3 can be attracted while the current is flowing through the coil, but it is very easy to attract the armature when the current is broken in the coi Thus itwill be seen that this modification is particularly adapted to circuits wherein it is desirous to have the relay energize only when the current through its coil is broken. t i

n Figo, I show a circuitemploying the relay of my invention. Relay 2l may be of either the types shown in Fig. 2 or in Figi and is used in series with the motor M to guard that motor against overload or no voltage release. The motor is a shunt Wound motor adapted to run on `a source of direct4 current which is brought into the terminals QG'and 27, the circuit leading through the break contacts 25, through the motor armature and field in parallel, through the winding of relay 2l to the opposite terminal. W hen the relay 2l is energized from either an overload current or break in the circuit, it closes A a circuit traceable from ground to spring 22 and it makes contact to the winding of relay to battery, energizing the relay 20, which upon energizing locks itself over a circuit from ground through key 28, through springs 2st, through the winding of the relay to battery. Relay 20 upon energizing opens the motor circuit at springs/2 5 and at spring 29 closes the obvious circuit to the signa-l 29 to notify the attendant that the motor -has been cut out of service.

`While l have chosen to show in connection with aparticular-type of relay, l have done so merely byway of example, as there are many modifications which can be made by one skilled in the art.;'without de# parting from the scope of my invention.

my invention What is claimed is l. An electromagnetic relay having. an armature, a core and a coil, an auxiliary netic element for preventing the attraction 0f said armature to said core when said coil is energized below or up to agiven value and for permitting attraction of said varmature to said core wheirsaid coil is deenergizing.

2. An electromagnetic relay having an armature, a core and a coil, a magneticshunt for preventing the attraction of said armature to said coil until said coil is energized by a current ot detinite `strength and means for A attracting said armature to said, core when said current is disconnected and said coil is deenergizing regardless of the strength of current used for energizing said coil.

3. An electromagnetic relay comprising a ycore and an armature, an air-gap between said core and armature, a main and an auxiliary magnetizing means on said core, a cornpletely closed magnetic shunt for said air gap attached to said core, the flux created by said main means flowing in two parallel paths in the same direction to prevent the attraction of said armature, one path including said shunt and excluding said air gap and the other path including said air gap, said auxilin opposition to said being attracted when said opposing fluxes in said shunt path are equal.

@An electromagnetic relay comprising a core and an armature mounted on a heel piece, an air-gap between said core and armature, two magnetizing means located on said core, a path ,for the flux created by one of. said means, comprising two parallel branches, one branch including and the other branch excluding said air-gap, a path for the flux createthby said other means also comprising two parallel branches both of which include said air-gap, the branch of said first path which excludes said air-gap being a completely closed magnetic circuit serving to prevent the attraction of said armature to said core while. said first magnetic means is energized by a current of constant Value.

5. ln an electromagneticrelay,.a core and an armature mounted on a heel piece, a memfirstiiux, said armaturel magv ber ot' n'iagnetizable material attached to said core serving as a back stop for the armature in said core, a secondary magnetic circuit for said main flux comprising the entire core, airarmature and air-gap, said primary gap, armature and heel-piece, means for energizing said auxiliaryl magnetizing means, a

lprimary magnetic circuit for the flux created -traction of said armature to said core whilev saidimam magnetizing means is energized. 65 In an electromagnetic relay, a core and an armature attached to a heel piece, a memtwo parallel paths for ber of magnetizable material attached to said core, and serving as a back stop for the armature in its normal position, an air-gap between said armature and core, a main magnetizing ineans located on the heel end otsaid core, means for energizing said magnetizing means,

the flux' created thereby, one of said paths being a completely'elosed magnetic circuit excluding said air-gap and the other pathincluding said air-gap, an auxiliary magnetizing means on the armature end of said core, said auxiliary means being inductively yenergized during the decay oi' the flux created by said main means, and two parallel 4paths for the flux created by said auxiliary means both includingsaidtair-gap, said l first flux being effective to prevent the attracing effective to attract tion of said armature, and said latter flux besaid armature to vsaid core. 4

. 7 In an velectromagnetic relay, a core and an armature attached to a heel piece', a member of magnetizable material attached to said core and servingY as a back stop for the armature inits normal position, an air-gap between said 'armature and core, a main magnetizing means located on the heel end of said core for creating 'a primary 'flux in a magnetic circuit comprising two parallel branches, oneof said branches beingA magnetically closed and the other branch including said-air-gap as a reluctance, an auxiliary magnetizing means on the armature end of said core responsive to the decaying of said primary another lux'eomprising two parallel branches both including said air-gap as a reluctance,

' said primary magnetically closed flux branch constituting a means for preventing the attraction of said armature by said main mag-" netizing means, and said auxiliary magnetizing means constituting a means for attracti y ing` said armature.

8. In an electromagnetic"relay, a core and an armature attached to a heel piece, acoil and acopper slug on saidl core, a member of' inagnetizable material att-aclied to said core between said coil and slug and serving as an armature back stop, said armature normally resting against said back stop, an air-'gap betweensaid. armature and core, 'a main magnetic circuit including said'core, air-gap,

flux for creating r to sustained current armature and heel piece, an auxiliary completely' closed magnetic circuit including part of said core, said back stop, armature and heel piece, said coreA when energized creating a .flux traversing said auxiliary completely closed magnetic circuit to prevent the attrac- 1 tion of said armature to said core, and during deenergization inductively creating a current in said copper slug lwhich produces a flux traversing said main magnetic circuit to attract said armature to said core.

9. .An electromagnetic relay, having a magnet and a normally open armature associated therewith, a primary magnetic circuit for the flux created through energ-'ization of said magnet by current connected thereto, a completely closed magnetic shunt circuit -or causing said flux to pass through said shunt, the parts beingso proportioned that said armature remains in its normal position on sustained current below orupto a value determined by tlie saturation point of said shunt,

' but closes at the disconnection of current at any value due to the flux in said shunt being reversed by inductive influence;

10. 'An electromagnetic relay comprising a magnetic circuit luctance, contact springs, an armature held in a normal position by said springs wherein said reluctance is maximum and movable to a position `wherein said reluctance is minifor creating-flux in saidA mum, a. winding magnetic circuit,V- a completely closed magnetic shunt circuit around-said reluctance and including said armature orforcing sai flux to passy through said shunt instead of through said reluctance to mature from beingl attracted While said coil is connected to sustained current below or up to a given value determined by the saturation point of said'shunt. y

ll. An' electromagnetic relay comprising a niagnetic circuit having i luctance, contact springs, an armature held in a normal position by said springs wherein said reluctance is maximumand movable to a position wherein said reluctance is minimum, a winding for creatingflux in said inagnctic circuit, ya completely closed'magnetic lshunt circuit around said reluctance and incliiding said armature for forcing-said flux to pass through said said reluctance to prevent said armature from being att below or up to a given value determined by the saturation point of said shunt, and electroconductxive means inductively responsive to. a-v disconnection of current from lsaid coil for creating a uX to move said armature regardless of the-current value at which said disconnection occurs, said armature in turn operating said contact springs.

having an air-gap as aref an air-gap as a reshunt instead of through 4 prevent said ar- 'acted whilesaid coil is connected i 12. An electromagnet having a movable to attract 13. An 10 and a coil Leeeyea for creati ng iux in a primary magneic circuit, an auxiliary magnetic circuit for preventing the attraction of said armature in said primary circuit when said coil isconnected to sustained Current, and means responsive to an interruption of currenJ in said coil for creating fiuX to atract said armature.

In Witness whereof, I hereunto subscribe my name this 23d day of July7 A. D9 1925,

JOHN ERIGKSUN. 

